Variation and diversity of the breakpoint sequences on 4AL for the 4AL/5AL translocation in Triticum.

The translocation of 4AL/5AL in Triticum, which occurred before the differentiation of T. urartu and einkorn, is an important chromosomal rearrangement. Recently, the first identification of breakpoint sequence on 4AL for this translocation provides the opportunity to analyze the variation and diversity of breakpoints in Triticum. In this study, the breakpoint regions of 52 accessions from 21 species were isolated and further characterized. The sequences were divided into 12 types based on their lengths, which ranged from 2009 to 2552 bp. Cluster analysis showed that they were further divided into three groups. Interesting evolutionary relationships among a few of the species were observed and discussed. Multiple sequence alignment of the 52 sequences made it possible to detect 13 insertion and deletion length polymorphisms (InDels) and 101 single nucleotide polymorphisms (SNPs). Furthermore, several species- or accession-specific SNPs or InDels were also identified. Based on BLAST analysis of the conserved sequences, the breakpoint was narrowed down to a 125 bp fragment. Taken together, the results obtained in this study enrich our understanding of chromosomal breakpoints and will be useful for the identification of other breakpoints in wheat.